An Introduction to Threat Modeling

There is no single solution for keeping yourself safe online. Digital security isn’t about which tools you use; rather, it’s about understanding the threats you face and how you can counter those threats. To become more secure, you must determine what you need to protect, and whom you need to protect it from. Threats can change depending on where you’re located, what you’re doing, and whom you’re working with. Therefore, in order to determine what solutions will be best for you, you should conduct a threat modeling assessment.

When Conducting an Assessment, There are Five Main Questions you Should Ask Yourself:

  1. What do you want to protect?
  2. Who do you want to protect it from?
  3. How likely is it that you will need to protect it?
  4. How bad are the consequences if you fail?
  5. How much trouble are you willing to go through in order to try to prevent those?

When we talk about the first question, we often refer to assets, or the things that you are trying to protect. An asset is something you value and want to protect. When we are talking about digital security, the assets in question are usually information. For example, your emails, contact lists, instant messages, and files are all assets. Your devices are also assets.

Write down a list of data that you keep, where it’s kept, who has access to it, and what stops others from accessing it.

In order to answer the second question, “Who do you want to protect it from,” it’s important to understand who might want to target you or your information, or who is your adversary. An adversary is any person or entity that poses a threat against an asset or assets. Examples of potential adversaries are your boss, your government, or a hacker on a public network.

Make a list of who might want to get ahold of your data or communications. It might be an individual, a government agency, or a corporation.

A threat is something bad that can happen to an asset. There are numerous ways that an adversary can threaten your data. For example, an adversary can read your private communications as they pass through the network, or they can delete or corrupt your data. An adversary could also disable your access to your own data.

The motives of adversaries differ widely, as do their attacks. A government trying to prevent the spread of a video showing police violence may be content to simply delete or reduce the availability of that video, whereas a political opponent may wish to gain access to secret content and publish it without you knowing.

Write down what your adversary might want to do with your private data.

The capability of your attacker is also an important thing to think about. For example, your mobile phone provider has access to all of your phone records and therefore has the capability to use that data against you. A hacker on an open Wi-Fi network can access your unencrypted communications. Your government might have stronger capabilities.

A final thing to consider is risk. Risk is the likelihood that a particular threat against a particular asset will actually occur, and goes hand-in-hand with capability. While your mobile phone provider has the capability to access all of your data, the risk of them posting your private data online to harm your reputation is low.

It is important to distinguish between threats and risks. While a threat is a bad thing that can happen, risk is the likelihood that the threat will occur. For instance, there is a threat that your building might collapse, but the risk of this happening is far greater in San Francisco (where earthquakes are common) than in Stockholm (where they are not).

Conducting a risk analysis is both a personal and a subjective process; not everyone has the same priorities or views threats in the same way. Many people find certain threats unacceptable no matter what the risk, because the mere presence of the threat at any likelihood is not worth the cost. In other cases, people disregard high risks because they don't view the threat as a problem.

In a military context, for example, it might be preferable for an asset to be destroyed than for it to fall into enemy hands. Conversely, in many civilian contexts, it's more important for an asset such as email service to be available than confidential.

Now, Let’s Practice Threat Modeling

If you want to keep your house and possessions safe, here are a few questions you might ask:

  • Should I lock my door?
  • What kind of lock or locks should I invest in?
  • Do I need a more advanced security system?
  • What are the assets in this scenario?
    • The privacy of my home
    • The items inside my home
  • What is the threat?
    • Someone could break in.
  • What is the actual risk of someone breaking in? Is it likely?

Once you have asked yourself these questions, you are in a position to assess what measures to take. If your possessions are valuable, but the risk of a break-in is low, then you probably won’t want to invest too much money in a lock. On the other hand, if the risk is high, you’ll want to get the best locks on the market, and perhaps even add a security system.

Last updated: 
2015-01-12
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